Don't be bashful! If you want comments, give comments. You don't need to be an expert photographer to express your opinion about the work of others. You don't need to go into great depth. A simple remark about cropping, composition, color, subject matter, etc. can be of just as much help to a budding photographer as an in-depth critique.
People are a continually fascinating source of subject matter. When people are the subjects of photographs, it’s usually their faces that hold our interest, as the human face is capable of an endless variety of expressions. Many of these expressions are fleeting, and photographers try to capture these moments before they disappear. Other times, people want to be memorialized in a formal portrait session. But no matter what the motivation is for doing portraiture, photographs of people tend to touch us more deeply than other subjects.